kono sigoto ha taihen desu kara, douryou no tasuke ga hituyou desu.

This is a very common question.

• 仕事は marks 仕事 as the topic of the sentence: as for this job / this work
• 助けが marks 助け as the thing that is needed

So the sentence is structured like this:

• この仕事は大変ですから = Because this job is tough
• 同僚の助けが必要です = coworkers’ help is necessary

With 必要です, the thing that is necessary is often marked with が.

So:

• 助けが必要です = help is necessary
• not 助けは必要です in the neutral/basic version

Using は and が this way is very natural in Japanese: one marks the overall topic, and the other marks the specific thing being described.

Here, 大変 means something like:

• hard
• tough
• difficult
• demanding

So この仕事は大変です means This job is tough or This work is difficult.

A useful thing to know is that 大変 can mean different things depending on context:

• 大変です = It’s tough / serious
• 大変な仕事 = a difficult job
• 大変！ = Oh no! / This is terrible!

So in this sentence, it does not mean very. It means the job itself is hard.

Because 大変 is functioning like a na-adjective or adjectival noun here, and in polite speech it is followed by です.

So:

• この仕事は大変です = polite
• この仕事は大変だ = plain

This is similar to:

• 静かです = is quiet
• 便利です = is convenient
• 必要です = is necessary

So even though 大変 may look like a noun or adverb in other contexts, here it behaves as a descriptive word and needs です in polite style.

から means because or since.

It connects the reason to the result:

• この仕事は大変ですから = Because this job is hard
• 同僚の助けが必要です = help from coworkers is necessary

So the whole sentence means:

• Because this job is tough, I need help from my coworkers or more literally
• Because this work is difficult, coworkers’ help is necessary

In polite speech, から often comes after a polite form like です:

• 大変ですから

That is completely natural.

Both から and ので can mean because, but they have a slightly different feel.

• から can sound a little more direct, personal, or assertive
• ので often sounds a little softer and more explanatory

So these are both possible:

• この仕事は大変ですから、同僚の助けが必要です。
• この仕事は大変なので、同僚の助けが必要です。

The version with ので may sound a bit gentler.
The version with から is still perfectly natural.

For learners, a simple rule is:

• use から for a straightforward because
• use ので when you want a slightly softer tone

同僚の助け means the help of coworkers or help from coworkers.

Breaking it down:

• 同僚 = coworker / colleague
• の = connects the two nouns
• 助け = help, assistance

So A の B often means one of these:

• B belonging to A
• B related to A
• B from A

Here it means:

• help from coworkers
• coworkers’ help

It does not necessarily mean only one coworker. Japanese often does not mark plural unless necessary, so 同僚 can mean coworker or coworkers depending on context.

Because the grammar pattern here is X が 必要です = X is necessary.

That means the thing before 必要です should be a noun-like expression.
助け is a noun meaning help or assistance.

So:

• 助けが必要です = help is needed

If you used a verb, you would need a different structure.

For example:

• 同僚に助けてもらう必要があります = I need to get help from my coworkers
• 同僚に手伝ってもらう必要があります = I need my coworkers to help me

Those are possible, but they are grammatically different and a bit more specific.

Because Japanese often leaves out the subject when it is understood from context.

In English, we often say:

• I need help from my coworkers

In Japanese, if it is obvious who is speaking or who the sentence is about, you usually do not need to say 私は.

So:

• 同僚の助けが必要です

can naturally mean:

• I need help from my coworkers
• we need help from our coworkers
• help from coworkers is necessary

depending on context.

Japanese prefers omission when the meaning is already clear.

It can be either, depending on context.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do.

So 同僚 can mean:

• a coworker
• coworkers

In this sentence, English would often translate it as coworkers because that sounds more natural:

• I need help from my coworkers

If you really wanted to emphasize plural in Japanese, you might sometimes use extra wording, but most of the time Japanese simply leaves it unmarked.

必要です means is necessary / is needed, and it is a very common, slightly formal or neutral way to say that something is needed.

So:

• 同僚の助けが必要です = help from coworkers is necessary / needed

You could also say:

• 同僚の助けが要ります

but 要る is less common in polite written or formal-style statements like this one.

Also, 必要です sounds a bit more objective and fits well with the tone of the sentence.

So this sentence has a fairly standard, polite, neutral feel.

この means this, and it must be followed by a noun.

So:

• この仕事 = this job / this work

You cannot say この by itself to mean this one.
If you want to say this one, you would use これ.

Compare:

• この仕事 = this job
• これ = this

So in the sentence, この directly modifies 仕事.

Yes, it can.

The original sentence is:

• この仕事は大変ですから、同僚の助けが必要です。

You could also say:

• 同僚の助けが必要です。この仕事は大変ですから。

This still means roughly the same thing, but the flow changes:

• the original gives the reason first, then the conclusion
• the reversed version gives the conclusion first, then the reason

In Japanese, putting the reason first with から is very common and sounds natural.

It is polite, standard Japanese.

That is because it uses:

• です
• 必要です

So it would be appropriate in many normal situations, such as conversation with coworkers, a teacher, or in general polite speech.

A plain-style version would be:

• この仕事は大変だから、同僚の助けが必要だ。

That sounds less formal and more casual.

So the original sentence is a good standard polite form for learners to know.